Method for pressing groove section with bending angle smaller than or equal to 90 degrees

ABSTRACT

A method and an apparatus or pressing groove section with a bending angle smaller than or equal to 90 degrees are provided. The apparatus comprises an upper convex die and a lower concave die are used for processing. The convex die comprises an expansion sleeve and an expansion core which are nested with each other. At least one of a central hole of the sleeve body and the core body is a wedge with a larger top and a smaller bottom, and a relative locking mechanism is arranged between the core body and the core body. The concave die comprises a multi-petal-shaped inner concave die and an external outer concave die which are in elastic connection.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/CN2015/098074 with a filing date of Dec. 21, 2015, designating the United States, now pending, and further claims priority to Chinese Patent. Application No. 201510141211.1 with a filing date of Mar. 27, 2015. The content of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the technical field of die processing, and particularly relates to a method for pressing a groove section with a bending angle smaller than or equal to 90 degrees.

BACKGROUND OF THE PRESENT INVENTION

At present, household electrical appliances, instruments, automobiles and other industries are brought into a mass production state. Many parts are only processed by machines, so that time and labor are consumed, precision is difficult to be guaranteed, and even some irregular parts cannot be processed at all. For example, a current deep groove type workpiece smaller than or equal to 90 degrees cannot be bent by a bending machine. At present, a common method is a welding and splicing method. A produced workpiece is often easy to deform and needs to be manually corrected. Therefore, the method is time- and labor-consuming, and the processed workpiece is non-standard and easy to deform. Therefore, the current processing method is very undesirable.

In view of this, the present invention is particularly proposed.

SUMMARY OF PRESENT INVENTION

A technical problem to be solved in the present invention is to overcome defects in the prior art, so as to provide a method for pressing a groove section with a bending angle smaller than or equal to 90 degrees.

In order to solve the above technical problem, a basic concept of a technical solution adopted in the present invention is as follows:

According to the method for pressing the groove section with the bending angle smaller than or equal to 90 degrees, a pressing apparatus comprises an upper die assembly and a lower die assembly which are coaxially arranged, wherein the upper die assembly comprises an expansion sleeve which is of a multi-petal-shaped structure in elastic connection and which has an outer part provided with a wedge die having a narrower top and a wider bottom, and an expansion core. In a central hole of the expansion sleeve, at least one of the central hole of the expansion sleeve and the expansion core is a wedge having a larger top and a smaller bottom. A height of a lowest point of the expansion core in a non-pressed initial state is greater than a height of a lowest point of the expansion sleeve. The expansion core is in clearance fit with the expansion sleeve, and a relative locking mechanism is arranged between the expansion core and the expansion sleeve. The relative locking mechanism is as follows: a transverse supporting rod is connected among petal bodies opposite to the expansion sleeve; the expansion core is of a structure with a longitudinal chute in a middle; an elastic part is arranged in the longitudinal chute; the transverse supporting rod penetrates through the longitudinal chute of the expansion core; and a bottom of the elastic part is pressed against the transverse supporting rod in the longitudinal chute of the expansion core. The lower die assembly comprises an inner concave die comprising a multi-petal-shaped structure in elastic connection, wherein a groove of the inner concave die is a wedge-shaped groove matched with the expansion sleeve in an outer shape to enable the expansion sleeve to enter the groove of the inner concave die; and an outer concave die, wherein a groove of the outer concave die is of a structure having a wider top and a narrower bottom; the inner concave die is arranged in the outer concave die; and an elastic body is arranged in the groove of the outer concave die and below the inner concave die.

The pressing, method comprises:

1) assembling an upper die assembly on a stamping mechanism connected with an expansion core of the upper die assembly, and laying a flat-plate type, workpiece to be processed at an upper port of the lower die assembly;

2) descending the stamping mechanism to drive an expansion sleeve and the expansion core of the upper die assembly to descend synchronously, wherein the expansion sleeve is contacted with the workpiece to be processed firstly during the descent: further descending the stamping mechanism, wherein the expansion core is further driven to descend while the expansion sleeve stops moving during the further descent since a stamping force of the stamping machine does not reach yield strength of the workpiece to be processed at this time, an elastic part in a chute of the expansion core is shrunk, and the workpiece is not bent; and expanding the expansion sleeve when the expansion core is descended to a bottom of the expansion sleeve, wherein the expansion core is contacted with the workpiece to be processed;

3) further descending the stamping mechanism, wherein the stamping force of the stamping machine exceeds the yield strength of the workpiece to be processed, and the expansion sleeve and the expansion core bend the workpiece together to allow the workpiece to enter a groove of an inner concave die;

4) further descending the stamping mechanism, wherein the inner concave die is descended when the stamping force exceeds a resistance of an elastic body at a bottom of the inner concave die, the inner concave die is compressed inwards by an outer concave die along with descent of the inner concave die, and when the inner concave die is descended to a termination point at the bottom of the outer concave die, the workpiece is tightly extruded and hooped on an outer wall of the inner concave die to form a preset grooved part; and

5) the elastic body at the bottom of the inner concave die being subjected to elastic recovery to bounce, the inner concave die upwards; meanwhile, the elastic part in the chute of the expansion core recovering deformation; and the expansion core and the, expansion sleeve relatively moving to recover to initial states; wherein along with continuous ascent of the inner concave, die, a groove width of the inner concave die is gradually enlarged, after the elastic body completely recovers the deformation, the inner concave die recovers to an initial position, the expansion sleeve, and the expansion core are taken out of the groove of the inner concave die of a lower die assembly under a pull-up force of the stamping mechanism, and then the workpiece is taken out.

Preferably, the elastic connection is realized among a plurality of petal bodies of the expansion sleeve through a structure as follows: the petal bodies opposite to the expansion sleeve are connected through a transverse spring rod; the spring rod comprises the transverse supporting rod and a spring; and a specific connecting relationship of the expansion sleeve and the spring rod is as follows: stepped holes having smaller interiors and larger exteriors are formed in inner walls of the petal bodies of the expansion sleeve; two ends of the transverse supporting rod respectively stretch into the stepped holes of the petal bodies on two sides; the spring is assembled at the end of the transverse supporting rod stretching into a larger hole of the stepped holes; limiting retainer rings are arranged at two ends of the spring at each end; and a size of a limiting retainer ring on an inner side is larger than a hole diameter of a smaller hole of the stepped holes.

Preferably, the elastic connection is realized among the plurality of petal bodies of the expansion sleeve in a manner of peripheral series connection by elastic parts.

Preferably, the relative locking mechanism further comprises an ascending stop auxiliary locking mechanism of the expansion core relative to the expansion sleeve. The ascending stop auxiliary locking mechanism is specifically as follows: an expanding cap larger than an upper size is arranged at the bottom of the expansion core, a flaring larger than an upper part is formed at the bottom of the central hole of the expansion, sleeve, and the expanding cap is matched with the flaring.

In the step 5), the expanding cap of the expansion core provides a pull-up force for the expansion sleeve when the expansion sleeve and the expansion core recovering to the initial states are taken out of the groove of the inner concave die of the lower die assembly by the stamping mechanism.

Preferably, a bottom of the expanding cap is, a flat bottom. Preferably, the central hole of the expansion sleeve and the expansion core are wedges each having a larger top and a smaller bottom. Preferably, an outer longitudinal section of the inner concave die is a trapezoid having a larger top and a smaller bottom, and inclination of an outer wall of the longitudinal section is matched with inclination of a groove wall of the groove of the outer concave die. Preferably, a positioning block is arranged at the bottom of the groove of the outer concave die and is a descending termination point of the inner concave die. Preferably, the outer concave die is of a multi-petal-shaped structure, and exteriors of the plurality of petals are supported through transverse adjustable supporting rods.

An external thread is arranged at the end of the transverse support connected with the multi-petal-shaped expansion sleeve. The external thread is arranged on an outer side of the limiting retainer rings. An adjusting nut is arranged and matched the extern thread of the transverse supporting rod.

Preferably, the stamping mechanism the pressing machine.

After the above technical solution is adopted, compared with the prior art, the present invention has beneficial effects as follows: the workpiece is processed by utilizing dies, thereby realizing simple processing course, high efficiency, standard produced workpiece and difficulty to deform, avoiding correction trouble and saving cost.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an overall structure the present invention;

FIG. 2 is a sectional view of an upper die assembly and a lower die assembly before pressing in the present invention;

FIG. 2a is a sectional view of a first member of an expansion sleeve;

FIG. 2b is a part-A enlarged drawing of FIG. 2 a;

FIG. 2c is a front view of an expansion core;

FIG. 2d is an A-A view of FIG. 2 a;

FIG. 3 is a sectional view of an upper die assembly and a lower die assembly when the upper die assembly is just contacted with a workpiece to be processed during stamping;

FIG. 4 is a sectional view of an upper die assembly and a lower die assembly when an elastic body at a bottom of an inner concave die does not deform during stamping:

FIG. 5 is a sectional view of an upper die assembly and a lower die assembly during pressing formation of a workpiece; and

FIG. 6 is a sectional view of an upper die assembly and die assembly when an elastic body at a bottom of n inner concave die recovers elastic deformation during material returning.

In the figures:

1-stamping press; 2-upper die assembly; 3-lower die assembly; 4-workpiece to be processed; 5-backing plate; 6-mounting seat; 21-first member; 211-stepped hole; 22-second member; 23-longitudinal chute; 24-expansion core; 25-spring rod; 251-transverse supporting rod; 252-spring; 26-elastic part; 241-expanding cap; 271-outside limiting retainer ring; 272-inside limiting retainer ring, 273-adjusting nut; 311-first inner concave die member, 312-second inner concave die member; 313-connecting elastic body; 314-anti-wear backing plate; 315-wear-resistant sliding rail; 321-first outer concave die member; 322-second outer concave die member; 323-elastic body in groove of outer concave die; 324-positioning block; and 325-adjustable supporting rod.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is further described below in combination with drawings and specific embodiments for understanding contents of the present invention. A method in the present invention is illustrated below by processing a grooved workpiece with two side surfaces and a grooved workpiece with four side surfaces. A processing apparatus is introduced first as follows:

With reference to FIG. 2, an apparatus for pressing a groove section with a bending angle smaller than or equal to 90 degrees comprises an upper die assembly 2 and a lower die assembly 3 which are coaxially arranged, wherein the upper die assembly 2 comprises an expansion sleeve which is of a multi-petal-shaped structure in elastic connection and which has an outer part provided with a wedge die having a narrower top and a wider bottom, and an expansion core 24. In a central hole of the expansion sleeve, at least one of the central hole of the expansion sleeve and the expansion core 24 is a wedge having a larger top and a smaller bottom. A height of a lowest point of the expansion core 24 in a non-pressed initial state is greater than a height of a lowest point of the expansion sleeve. The expansion core 24 is in clearance fit with the expansion sleeve, and a relative locking mechanism arranged between the expansion core and the expansion sleeve. The relative locking mechanism is as follows: a transverse supporting rod 251 is connected among petal bodies opposite to the expansion sleeve; the expansion core 24 is of a structure with a longitudinal chute 23 in the middle; an elastic part 26 is arranged in the longitudinal chute 23; the transverse supporting rod 251 penetrates through the longitudinal chute 23 of the expansion core; and a bottom of the elastic part 26 is pressed against the transverse supporting rod 251 in the longitudinal chute 23 of the expansion core. The lower die assembly comprises: an inner concave die comprising a multi-petal-shaped structure in elastic connection, wherein a groove of the inner concave die is a wedge-shaped groove matched with the expansion sleeve in an outer shape to enable the expansion sleeve to enter the groove of the inner concave die; and an outer concave die, wherein a groove of the outer concave die is of a structure having a wider top and a narrower bottom; the inner concave die is arranged in the outer concave die; and an elastic body 323 is arranged in the groove of the outer concave die and below the inner concave die.

With reference to FIG. 1, the pressing apparatus in the present invention takes an existing stamping press as a driving mechanism, and a pressing machine slide block is connected with a top of the expansion core.

A process is illustrated below through a method for processing the grooved workpiece with two side surfaces and the grooved workpiece with four side surfaces in the present invention.

Processing apparatuses in the following two embodiments are based on the above structure.

Embodiment 1 Processing of the Grooved Workplace with Two Side Surfaces

FIG. 2-FIG. 6 are structural schematic diagrams of each processing step of the processing apparatus. The expansion sleeve comprises a pair of a first member 21 and a second member 22 opposite to each other. The first member 21 and the second member 22 are plates which are thin in tops and thick in bottoms and are gradually inclined to two sides from top to bottom. The first member 21 and the second member 22 are connected through a transverse spring rod 25, and the transverse spring rod 25 comprises a transverse supporting rod 251 and a spring 252.

A specific connecting relationship of the expansion sleeve and the spring rod 25 is as follows: in combination with FIG. 2a and FIG. 2 b, stepped holes 211 having smaller interiors and bigger exteriors are formed in inner walls of the first member 21 and the second member 22; two ends of the transverse supporting rod respectively stretch into the stepped holes 211 of the members on two sides; the spring 252 is assembled at the end of the transverse supporting rod stretching into a larger hole of the stepped holes; limiting retainer rings 271 and 272 are arranged at two ends of the spring 252 at each end; a size of the limiting retainer ring 272 on an inner side is larger than a hole diameter of a smaller hole of the stepped holes; an external thread is arranged at the end of the transverse supporting rod and arranged on an outer side of the limiting retainer rings; and an adjusting nut 273 is arranged and matched with the external thread of the transverse supporting rod. Through the adjusting nut 273, a width of the expansion sleeve is adjustable, thereby processing the grooved workpieces of different groove widths.

A two-sided structure having a narrower top and a wider bottom in elastic connection is formed at an outer part of the connected expansion sleeve, and the central hole of the expansion sleeve is a wedge-shaped hole having ,a larger top and a smaller bottom.

The expansion core 24 is also a wedge having a larger top and a smaller bottom. A longitudinal section of the expansion core is shown in FIG. 2d . The expansion core 24 and the central hole of the expansion sleeve are wedge-shaped, and surface contact between the expansion core and the expansion sleeve can be ensured when the expansion core descends to expand the expansion sleeve, thereby preventing the expansion core from wearing the expansion sleeve.

With reference to FIG. 2c and FIG. 2d , the expansion core 24 is of structure with a longitudinal chute 23 in a middle; an elastic part 26 (which may be an ordinary spring in FIG. 2 to FIG. 6) is arranged in the longitudinal chute 23 of the expansion core; the spring rod 25 penetrates through the longitudinal chute 23 of the expansion core; and a bottom of the elastic part 26 is pressed against the spring rod 25 in the longitudinal chute 23 of the expansion core. A quantity of chutes is designed according to a length of the expansion core and a width of a workpiece to be processed 4. For example, three transverse chutes arranged in parallel, and three spring rods 25 are designed. Through the arrangement of a plurality of chutes and a plurality of spring rods 25, a force may be simultaneously applied to the workpiece to be processed 4 at multiple points. For a wider workpiece to be processed 4, each point of the workpiece may generate a downward pressure, so that the processed workpiece is more standard, and physical properties of the workpiece are not damaged by point-to-point tearing and pulling.

A structure among a plurality of petals of the expansion sleeve connected by the spring rod as well as the longitudinal chute of the expansion core and a structure of an elastic part in the chute form elastic connection between the above relative locking mechanism and the expansion sleeve.

The relative locking mechanism further comprises an ascending stop auxiliary locking mechanism of the expansion core relative to the expansion sleeve. The ascending stop auxiliary locking mechanism is specifically as follows: an expanding cap 241 larger than an upper size is arranged at the bottom of the expansion core 24, a flaring larger than an upper part is formed at the bottom of the central hole of the expansion sleeve, and the expanding cap 241 is matched with the flaring. A height of the expanding cap 241 of the expansion core 24 is smaller than a longitudinal depth of the flaring at the bottom of the expansion sleeve, thereby ensuring that the height of a lowest point of the expansion core in the non-pressed initial state is greater than a height of a lowest point of the expansion sleeve.

A bottom of the expanding cap 241 is a flat bottom, so that a larger plane is formed at the bottoms of the expansion core and the expansion sleeve when the expansion core is pressed to the bottommost end, thereby ensuring that a groove bottom of the processed workpiece is flat.

The inner concave die comprises a first inner concave die member 311 and a second inner concave die member 312. A longitudinal section of each of the first inner concave die member 311 and the second inner concave die member 312 is of a bending structure with an interior angle smaller than 90 degrees, and the bending structure is similar to an “L”-shaped structure with a bending angle smaller than 90 degrees. The first inner concave, die member 311 and the second inner concave die member 312 are arranged in a groove of the outer concave die opposite to each other. A connecting elastic body 313 (which may be an ordinary spring in FIG. 2 to FIG. 6) is arranged between bottoms of the first inner concave die member 311 and the second inner concave die member 312. A lower side of an outer wall of the inner concave die is inclined inwards, so that a longitudinal section of an outer part of the inner concave die is of a trapezoid having a larger top and a smaller bottom. Inclination of the outer wall is matched with inclination of a groove wall of the groove of the outer concave die so that the inner concave die can be attached to the outer concave die under an action of the connecting elastic body 313, and then the workpiece may be well extruded.

A spliced joint is formed at the bottoms of the first inner concave die member 311 and the second inner concave die member 312. An elastic body 323 is respectively arranged below each of the two inner concave die members, thereby ensuring ascending and descending consistency of the first inner concave die member 311 and the second inner concave die member 312 of the inner concave die and bringing convenience to processing of the workpiece.

Anti-wear backing plates and wear-resistant sliding rails are sequentially arranged at the bottom of the groove of the inner concave die from top to bottom. The wear-resistant sliding rails and the anti-wear backing plates are sequentially arranged between the inner concave die and the elastic body 323 at the bottom of the inner concave die from top to bottom.

The wear-resistant sliding rails and the anti-wear backing plates are arranged for reducing friction force between the workpiece and the inner concave die and between the inner concave die and the backing plates during bending forming of the workpiece, thereby avoiding wearing the apparatus.

The outer concave die comprises a first outer concave die member 321 and a second outer concave die member 322. A longitudinal section of each of the first outer concave die member 321 and the second outer concave die member 322 is of a bending structure with an interior angle slightly larger than 90 degrees, and the bending structure is similar to an “L”-shaped structure with an interior angle larger than 90 degrees. The first outer concave die member 321 and the second outer concave die member 322 are oppositely arranged on a backing plate of an operating platform of a pressing machine. Exteriors of the first outer concave die member 321 and the second outer concave die member 322 are respectively supported through adjustable supporting rods 325 mounted on mounting seats 6 at two ends of a backing plate 5. The backing plate 5 is arranged on a worktable of the pressing machine, One end of each of the supporting rods 325 is in threaded connection with the mounting seats 6 and fastened by nuts, so that the two outer concave die members are combined into a grooved frame of the>outer concave die. The groove width of the outer concave die can be adjusted by adjusting a length of a screw rod.

Preferably, upper ends of the inner concave die and the outer concave die are flush with each other in the non-pressed initial state. A positioning block 324 is arranged at the bottom of the groove of the outer concave die. The method for processing the grooved workpiece with the two side surfaces is as follows;

1. with reference to FIG. 1, the upper die assembly is assembled on a pressing machine; a slide block of the pressing machine is connected with a top end of the expansion core; and a flat-plate type workpiece to be processed 4 is laid at an upper port of the lower die assembly (laid at an upper port of the outer concave die in the present embodiment); at this moment, an outside dimension of the expansion sleeve is a1, a1 is a minimum, the groove width of the inner concave die is b1 and b1 is a maximum;

2. with reference to FIG. 3, when pressing is needed, the slide block of the pressing machine is descended to drive the expansion core and the expansion sleeve to be synchronously descended; the expansion sleeve is contacted with the workpiece to be processed 4 firstly; and the slide block of the pressing machine is continuously descended; at this moment, a stamping force of the pressing machine does not reach yield strength of the workpiece to be processed 4; therefore, at this moment, only the expansion core is continuously descended, the expansion sleeve is not moved, the elastic part in the chute of the expansion core is shrunk and the workpiece is not bent when the expansion core descends to the bottom of the expansion sleeve, the expansion sleeve is expanded, and the expansion core is also contacted with the workpiece to be processed; and at this moment, the outside dimension of the expansion sleeve is a2, a2 is a maximum and is more than a1, the groove width of the inner concave die is b2, and b2 is equal to b1;

3. with reference to FIG. 4, the slide block of the pressing machine is continuously descended; the stamping force of the pressing machine exceeds the yield strength of the workpiece to be processed; and the expansion sleeve and the expansion core bend the workpiece together to allow the workpiece to enter the groove of the inner concave die (in order to enable the workpiece to be processed 4 to enter the deep groove of the die, the groove width of the die at an initial position should be slightly greater than a width of a lower end of the expansion core during an actual operation); and at this moment, the outside dimension of the expansion sleeve is a3, a3 is equal to the a2, the groove width of the inner concave die is, b3, and b3 is equal to the b1;

4. with reference to FIG. 5, the slide block of the pressing machine is continuously descended; the inner concave die is descended when the force exceeds resistance of the elastic body 323 at the bottom of the inner concave die: the inner concave die is compressed inwards by the outer concave die along with descending of the inner concave die; the connecting elastic body 313 between the inner concave dies is shrunk; and when the inner concave die descends to the positioning block (that is, a termination point) at the bottom of the outer concave die, the groove width of the inner concave die is a minimum; the workpiece is tightly extruded and hooped on an, outer wall of the inner concave die to form a preset grooved part; and at this moment, the outside dimension of the expansion sleeve is a4, and a4 is equal to a2 and a3; the groove width of the inner concave die is b4 and b4 is a minimum and less than b3; and the groove width of the workpiece is, a minimum; and

5. material returning: with reference to FIG. 6, the elastic body 323 at the bottom of the inner concave die is subjected to elastic recovery; the inner concave die upwards bounces; the elastic part in the chute of the expansion core recovers deformation; the expansion core and the expansion sleeve relatively move to recover to the initial states; and along with continuous ascending of the inner concave die, the groove width of the inner concave die is gradually enlarged; and after the elastic body 323 completely recovers the deformation, the inner concave die recovers to the initial position; the groove width reaches a maximum; the expansion sleeve and the expansion core are taken out of the groove of the lower die assembly under a pull-up force of the slide block of the pressing machine; and then the workpiece is taken out; because the groove width of the workpiece is a minimum at this moment, the groove width, of the inner concave die is b5 and b5 is equal to the b1 and is a minimum, while the groove width of the outer concave die (that is, the outside dimension of the expansion sleeve) is a5, and a5 is equal to a1 and is a maximum. Therefore, the upper die assembly can be easily taken out of the lower die assembly, and the workpiece can be easily taken out. When the upper die assembly is taken out of the lower die assembly by the slide block of the pressing machine, on one hand, by virtue of a connecting action of the spring rod, the expansion core and the elastic part in the longitudinal chute of the expansion core, and on the other hand, by virtue of pull-up force for pulling up the expansion sleeve through the expanding cap, the upper die assembly is completely taken out of the lower die assembly due to the coaction, so that the spring rod can be prevented from being deformed by applied force, thereby ensuring that the upper die assembly is effectively taken out.

Embodiment 2 Processing of the Grooved Workpiece with Four Side Surfaces

The expansion sleeve comprises a first member and a second member opposite to each other as well as a third member and a fourth member opposite to each other. The four members are plates which are thin in tops and thick in bottoms and are gradually inclined to, two sides from top to bottom. The four members are encircled to form a rectangular pyramid shape without a top. The four members are connected through transverse spring rods, and the spring rods comprise transverse supporting rods and springs; and a specific connecting relationship of the expansion sleeve and the spring rods is as follows: stepped holes having smaller interiors and larger exteriors are formed in inner walls of the first member, the second, member, the third member and the fourth member; a crossed transverse supporting rod is arranged; four ends of the crossed transverse supporting rod respectively stretch into the stepped holes of the four members; the springs care assembled at the ends of the transverse supporting rods stretching into larger holes of the stepped holes; limiting retainer rings are arranged at two ends of the spring at each end; a size of the limiting retainer ring on an inner side is, larger than a hole diameter of a smaller hole of the stepped holes; an external thread is arranged at the end of each transverse supporting rod and arranged on an outer side of the limiting retainer ring; and an adjusting nut is arranged and matched with the external thread of the transverse supporting rod. Through the adjusting nut, a width of the expansion sleeve is adjustable, thereby processing of the grooved workpieces of different groove widths. A four-sided structure having a narrower top and a wider bottom in elastic connection is formed at an outer part of the connected expansion sleeve, and the central hole of the expansion sleeve is a wedge-shaped hole having a larger top and a smaller bottom. The expansion core is a quadrilateral prism frustum having a larger top and a smaller bottom, and through the shape, surface contact between the expansion core and the expansion sleeve can be ensured when the expansion core descends to expand the expansion sleeve, thereby preventing the expansion core from wearing the expansion sleeve. The expansion core is of a structure with a longitudinal chute in a middle; an elastic part (which may be an ordinary spring) is arranged in the longitudinal chute of the expansion core; intersections of the four transverse supporting rods are positioned in the longitudinal chute of the expansion core; and a lower end of the elastic part is pressed against the intersections of the four transverse supporting rods.

A structure among a plurality of petals of the expansion sleeve connected by the spring rod, the longitudinal chute of the expansion core and a structure of an elastic part in the chute form elastic connection between the above relative locking mechanism and the expansion sleeve.

The relative locking mechanism further comprises an ascending stop auxiliary locking mechanism of the expansion core relative to the expansion sleeve. The ascending stop auxiliary locking mechanism is specifically as follows: an expanding cap, larger than an upper size is arranged at the bottom of the expansion core; a flaring larger than an upper part is formed at the bottom of the central hole of the expansion sleeve; and the expanding cap is matched with the flaring. A height of the expanding cap of the expansion core is smaller than a longitudinal depth of the flaring at the bottom of the expansion sleeve, thereby ensuring that the height of a lowest point of the expansion core in the non-pressed initial state is greater than a height of a lowest point of the expansion sleeve.

A bottom of the expanding cap is a flat bottom, so that a larger plane is formed at the bottoms of the expansion core and the expansion sleeve when the expansion core is pressed to the bottommost end, thereby ensuring that a groove bottom of the processed workpiece is flat.

The inner concave die comprises a first inner concave die member, a second inner concave die member, a third inner concave die member, a fourth inner concave die member, a fifth inner concave die member and a sixth inner concave die member. A longitudinal section of each of the six inner concave die members is of a bending structure with an interior angle slightly smaller than 90 degrees, and the bending structure is similar to an “L”-shaped structure with a bending angle smaller than 90 degrees. The first inner concave die member and the second inner concave die member are opposite to each other; the third inner concave the member and the fourth inner concave die member are oppositely arranged on two sides of the first inner concave die member; the fifth inner concave die member and the sixth inner concave die member are oppositely arranged on two sides of the second inner concave die member; and the six inner concave die members are arranged in the groove of the outer concave die.

A connecting elastic body, is respectively arranged between bottoms of the first inner concave die member and the second inner concave die member, between bottoms of the first inner concave die member and the third inner concave die member, between bottoms of the first inner concave the member and the fourth inner concave die member, between bottoms of the second inner concave die member and the fifth inner concave die member and between bottoms of the second inner concave die member and the sixth inner concave die member. The six inner concave die members enable the inner concave die to form an enlargeable and shrinkable four-sided grooved frame by virtue of the five connecting elastic bodies. A lower side of an outer wall of each of the six inner concave die members is inclined inwards, so that a quadrilateral prism is formed at an outer part of the inner concave die. Inclination of the outer wall is matched with inclination of a groove wall of the groove of the outer concave die, so that the inner concave die can be attached to the outer concave die under actions of the connecting elastic bodies, thereby better extruding the workpiece.

Spliced joints are formed at the bottoms of the six inner concave die members. An elastic body is respectively arranged below each of the six inner concave die members, thereby ensuring descending consistency of the six inner concave die members of the inner concave die and bringing convenience to processing of the workpiece. Anti-wear backing plates and wear-resistant sliding rails are sequentially arranged at the bottom of the groove of the inner concave die from top to bottom. The wear-resistant sliding rails and the anti-wear backing plates are sequentially arranged between the inner concave die and the elastic body at the bottom of the inner concave die from top to bottom. The wear-resistant sliding rails and the anti-wear backing plates are arranged for reducing friction force between the workpiece and the inner concave die and between the inner concave die and the backing plates during bending forming of the workpiece, thereby avoiding wearing the apparatus. The outer concave die comprises a first outer concave die member, a second outer concave die member, a third outer concave die member, a fourth outer concave die member, a fifth outer concave die member and a sixth outer concave die member. A longitudinal section of each of the six outer concave die members is of a bending structure with an interior angle slightly larger than 90 degrees, and the bending structure is similar to an “L”-structure with a bending angle larger than 90 degrees. The first outer concave die member and the second outer concave die member are opposite to each other; the third outer concave die member and the fourth outer concave die member are oppositely arranged on two sides of the first outer concave die member; the fifth outer concave die member and the sixth outer concave die member are oppositely arranged on two sides of the second outer concave die member; and the six outer concave die members are arranged on the backing plates of the operating platform of the pressing machine. Exteriors of the six outer concave die members are respectively supported through adjustable supporting rods mounted on mounting seats at six ends of the backing plates. The backing plates are arranged on a worktable of the pressing machine. One end of each of the supporting rods is in threaded connection with the mounting seats on the backing plates and fastened by nuts, so that the six outer concave die members are combined into a grooved frame of the outer concave die. The groove width of the outer concave die can be adjusted by adjusting a length of a screw rod. In fact, preferably upper ends of the inner concave die and the outer concave die are flush with each other in the non-pressed initial state. A positioning block is arranged at the bottom of the groove of the outer concave die. The method for processing the grooved workpiece with the four side surfaces can refer to FIG. 2 to FIG. 6 as follows:

1. with reference to FIG. 2, the upper die assembly is assembled on a pressing machine; a slide block of the pressing machine is connected with a top end of the expansion core; a flat-plate type workpiece to be processed of which four corners are cut off is laid at an upper port of the lower die assembly (laid at an upper port of the outer concave die in the present embodiment); and at this moment, an outside dimension, of the expansion sleeve is a1, and a1 is a minimum; and the groove width of the inner concave die is b1, and b1 is a maximum;

2. with reference to FIG. 3, when pressing is needed, the slide block of the pressing machine is descended to drive the expansion core and the expansion sleeve to be synchronously descended; the expansion sleeve is contacted with the workpiece to be processed firstly; the slide block of the pressing machine is continuously descended; at this moment, a stamping force of the pressing machine does not reach yield strength of the workpiece to be processed; therefore, at this moment, only the expansion core is continuously descended; the expansion sleeve is not moved; the elastic part in the chute of the expansion core is shrunk; the workpiece is not bent; when the expansion core descends to the bottom of the expansion sleeve, the opening of the expansion sleeve is expanded and the expansion core is also contacted with the workpiece to be processed; and at this moment, the outside dimension of the expansion sleeve is a2, and a2 is a maximum and is greater than a1; and the groove width of the inner concave die is b2 and b2 is equal to the b1;

3. with reference to FIG. 4, the slide block of the pressing machine is continuously descended; the stamping force of the pressing machine exceeds the yield strength of the workpiece to be processed; and the expansion sleeve and the expansion core bend the workpiece together to allow the workpiece to enter the groove of the inner concave die (in order to enable the workpiece to be processed 4 to enter the deep groove of the die, the groove width of the die at an initial position should be slightly greater than a width of a lower end of the expansion core during an actual operation); and at this moment, the outside dimension of the expansion sleeve is a3, and a3 is equal to the a2; and the groove width of the inner concave die is b3, and b3 is equal to the b1;

4. with reference to FIG. 5, the slide block of the pressing machine is continuously descended; the inner concave die is descended when the force exceeds resistance of the elastic body at the bottom of the inner concave die; the inner concave die is compressed inwards by the outer concave die along with descending of the inner concave die; the connecting elastic body between the inner concave dies is shrunk; and when the inner concave die descends to the positioning block (that is, a termination point) at the bottom of the outer concave die, the groove width of the inner concave die is a minimum; the workpiece is tightly extruded and hooped on an outer wall of the inner concave die to form a preset grooved part; and at this moment, the outside dimension of the expansion sleeve is a4, and a4 is equal to a2 and a3; the groove width of the inner concave die is b4, and b4 is a minimum and less than b3; and the groove width of the workpiece is a minimum; and

5. material returning: with reference to FIG. 6, the elastic body at the bottom of the inner concave die is subjected to elastic recovery; the inner concave die upwards bounces; meanwhile, the elastic part in the chute of the expansion core recovers deformation; the expansion core and the expansion sleeve relatively move to recover to the initial states; along with continuous ascending of the inner concave die, the groove width of the inner concave die is gradually enlarged; and after the elastic body completely recovers the deformation, the inner concave die recovers to the initial position; the groove width also reaches the maximum; the expansion sleeve and the expansion core are taken out of the groove of the lower die assembly under a pull-up force of the slide block of the pressing machine; and then the workpiece is taken out; because the groove width of the workpiece is a minimum at this moment, the groove width of the inner concave die is b5 and b6 is equal to the b1 and is a minimum, while the groove width of the outer concave die (that is, the outside dimension of the expansion sleeve) is a5 and a5 is equal to a1 and maximum. Therefore, the upper die assembly can be easily taken out of the lower die assembly, and the workpiece can be easily taken out. When the upper die assembly is taken out of the lower die assembly by the slide block of the pressing machine, on one hand, by virtue of a connecting action of the spring rod, the expansion core and the elastic part in the longitudinal chute of the expansion core, and on the other hand, by virtue of pull-up force for pulling up the expansion sleeve through the expanding cap, the upper die assembly is completely taken out of the lower die assembly due to the coaction, so that the spring rod can be prevented from being deformed by applied force, thereby, ensuring that the upper die assembly is effectively taken out.

In the present invention, the workpiece is processed by utilizing the dies, thereby realizing simple processing course, high efficiency, standard produced workpiece and difficulty to deform, avoiding correction trouble and saving cost. The apparatus is driven by the pressing machine, thereby realizing automation of the entire apparatus. With adoption of the processing method of the apparatus, an effect of processing the deep-grooved workpiece is particularly obvious. According to the method in the present invention, a workpiece of 90 degrees can be processed, and the interior angle of the inner concave die only needs to be designed to be slightly larger, such as 88 degrees, 89 degrees etc. Since the processed workpiece is slightly expanded outwards, the interior angle of the expanded workpiece can reach 90 degrees.

Since the widths of the expansion sleeve and the outer concave die are adjustable, the workpieces of different groove widths can be processed by adjusting the groove widths of the expansion sleeve and the outer concave die.

According to Embodiment 2, a cylindrical workpiece with an angle smaller than or equal to 90 degrees is easily processed by virtue of proper deformation in the present invention.

When a multi-sided grooved workpiece or the cylindrical workplace is processed, the more the petals of the inner concave die are, the more perfect the processed workpiece is. Shapes of the expansion sleeve members, the inner concave die members and the outer concave die members may be other shapes and are not limited to above embodiments. The elastic body at the bottom of the inner concave die preferably adopts a polyurethane rubber block. An oil press, a hydraulic press and the like may be adopted in the method.

The elastic connection is realized among the plurality of petal bodies of the expansion sleeve in a manner of peripheral series connection by the elastic parts. For example, an elastic bracelet structure is formed. Compared with the relative locking mechanism and above embodiments, an independent transverse supporting rod can be matched with a related structure of the expansion core.

Steel plates and other workpieces can be processed by adopting the processing method of the present apparatus. Multi-sided grooved workpieces, such as five-sided and six-sided workpieces, can also be processed by adopting the processing method of the present apparatus. With respect to the above two embodiments, the expansion core may be a cube or a cuboid, while relative, to the above two embodiments, one disadvantage of the structure is that the expansion sleeve may be easily worn due to point contact between the expansion core and the expansion sleeve; or the central hole of the expansion sleeve is an equal-diameter hole, and the expansion core has a wedge shape. Certainly, the above wear problem may also exist.

The above embodiments are only preferred embodiments of the present invention. It should be indicated that those ordinary skilled in the art may make several improvements and modifications on premise of not deviating from principles of the present invention. These improvements and modifications should also be regarded as a protection scope of the present invention. 

We claim:
 1. An apparatus for pressing a groove section with a bending angle smaller than or equal to 90 degrees, comprising an upper die assembly and a lower die assembly which are coaxially arranged, wherein the upper die assembly comprises an expansion sleeve which is of a multi-petal-shaped structure in elastic connection and which has an outer part provided with a wedge die having a narrower top and a wider bottom, and an expansion core; in a central hole of the expansion sleeve, at least one of the central hole of the expansion sleeve and the expansion core is a wedge having a larger top and a smaller bottom; a height of a lowest point of the expansion core in a non-pressed initial state is greater than a height of a lowest point of the expansion sleeve; the expansion core is in clearance fit with the expansion sleeve, and a relative locking mechanism is arranged between the expansion core and the expansion sleeve; the relative locking mechanism is as follows: a transverse supporting rod is connected among petal bodies opposite to the expansion sleeve; the expansion core is of a structure with a longitudinal chute in a middle; an elastic part is arranged in the longitudinal chute; the transverse supporting rod penetrates through the longitudinal chute of the expansion core; and a bottom of the elastic part is pressed against the transverse supporting rod in the longitudinal chute of the expansion core; the lower die assembly comprises an inner concave die comprising a multi-petal-shaped structure in elastic connection, and an outer concave die; a groove of the inner concave die is a wedge-shaped groove matched with the expansion sleeve in an outer shape to enable the expansion sleeve to enter the groove of the inner concave die; a groove of the outer concave die is of a structure having a wider top and a narrower bottom; the inner concave die is arranged in the outer concave die; and an elastic body is arranged in the groove of the outer concave die and below the inner concave die.
 2. The apparatus according to claim 1, wherein the elastic connection is realized among the plurality of petal bodies of the expansion sleeve through a structure as follows: the petal bodies opposite to the expansion sleeve are connected through a transverse spring rod; the spring rod comprises the transverse supporting rod, and a spring: and a specific connecting relationship of the expansion sleeve and the spring rod is as follows: stepped holes having smaller interiors and larger exteriors are formed in inner walls of the petal bodies of the expansion sleeve; two ends of the transverse supporting rod respectively stretch into the stepped holes of the petal bodies on two sides; the spring is assembled at the end of the transverse supporting rod stretching into a larger hole of the stepped holes; limiting retainer rings are arranged at two ends of the spring at each end; and a size of a limiting retainer ring on an inner side is larger than a hole diameter of a smaller hole of the stepped holes.
 3. The apparatus according to claim 1, wherein the elastic connection is realized among the plurality of petal bodies of the expansion sleeve in a manner of peripheral series connection by elastic parts.
 4. The apparatus according to claim 3, wherein the relative locking mechanism further comprises an ascending stop auxiliary locking mechanism of the expansion core relative to the expansion sleeve; the ascending stop auxiliary locking mechanism is specifically as follows: an expanding cap larger than an upper size is arranged at the bottom of the expansion core, a flaring larger than an upper part is formed at the bottom of the central hole of the expansion sleeve, and the expanding cap is matched with the flaring.
 5. The apparatus according to claim 4, wherein a bottom of the expanding cap is a flat.
 6. The apparatus according to claim 1, wherein the central hole of the expansion sleeve and the expansion core are wedges each having a larger top and a smaller bottom.
 7. The apparatus according to claim 1, wherein an outer longitudinal section of the inner concave die is a trapezoid having a larger top and a smaller bottom, and inclination of an outer wall of the longitudinal section is matched with inclination of a groove wall of the groove of the outer concave die.
 8. The apparatus according to claim 1, wherein a positioning block is arranged at the bottom of the groove of the outer concave die and is a descending termination point of the inner concave die.
 9. The apparatus according to claim 2, wherein the outer concave die is of a multi-petal-shaped structure, and exteriors of the plurality of petals are supported through transverse adjustable supporting rods; and an external thread is arranged at the end of the transverse support connected with the multi-petal-shaped expansion sleeve; the external thread is arranged on an outer side of the limiting retainer rings and an adjusting nut is arranged and matched with the external thread of the transverse supporting rod.
 10. A method for pressing a groove section with a bending angle smaller than or equal to 90 degrees, comprising: 1) assembling an upper die assembly on a stamping mechanism connected with an expansion core of the upper die assembly, and laying a flat-plate type workpiece to be processed at an upper port of the lower die assembly; 2) descending the stamping mechanism to drive an expansion sleeve and the expansion core of the upper die assembly to descend synchronously, wherein the expansion sleeve is contacted with the workpiece to be processed firstly during the descent; further descending the stamping mechanism, wherein the expansion core is further driven to descend while the expansion sleeve stops moving during the further descent since a stamping force of the stamping machine does not reach yield strength of the workpiece to be processed at this time, an elastic part in a chute of the expansion core is shrunk, and the workpiece is not bent; and expanding the expansion sleeve when the expansion core is descended to a bottom of the expansion sleeve, wherein the expansion core is contacted with the workpiece to be processed; 3) further descending the stamping mechanism wherein the stamping force of the stamping machine exceeds the yield strength of the workpiece to be processed, and the expansion sleeve and the expansion core bend the workpiece together to allow the workpiece to enter a groove of an inner concave die; 4) further descending the stamping mechanism, wherein the inner concave die is descended when the stamping force exceeds a resistance of an elastic body at a bottom of the inner concave die, the inner concave die is compressed inwards by an outer concave die along with descent of the inner concave die, and when the inner concave die is descended to a termination point at the bottom of the outer concave die, the workpiece is tightly extruded and hooped on an outer wall of the inner concave die to form a preset grooved part; and 5) the elastic body at the bottom of the inner concave die being subjected to elastic recovery to bounce the inner concave die upwards; meanwhile, the elastic part in the chute of the expansion core recovering deformation; and the expansion core and the expansion sleeve relatively moving to recover to initial states; wherein along with continuous ascent of the inner concave die, a groove width of the inner concave die is gradually enlarged, after the elastic body completely recovers the deformation, the inner concave die recovers to an initial position, the expansion sleeve and the expansion core are taken out of the groove of the inner concave die of a lower die assembly under a pull-up force of the stamping mechanism, and then the workpiece is taken out.
 11. The method according to claim 10, wherein in the step 5), an expanding cap of the expansion core provides the pull-up force for the expansion sleeve when the expansion sleeve and the expansion core recovering to the initial states are taken out of the groove of the inner concave die of the lower the assembly by the stamping mechanism.
 12. The method according to claim 10, wherein the stamping mechanism is a pressing machine. 